Method to agglomerate metal particles and metal particles having improved properties

ABSTRACT

A method to agglomerate metal particles such as tantalum and niobium powders is described which includes combining a volatilizable or vaporizable liquid with the particles to form wet particles; compacting the wet particles; drying the compacted wet particles to form a cake; and heat treating the cake to form the agglomerated particles. Also described are agglomerated particles obtained by this method and further, particles, preferably tantalum or niobium powder, having a flow rate of at least about 65 mg/sec and/or an improved pore size distribution, and/or a higher Scott Density. Capacitors made from tantalum powder and niobium powder are also described.

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/921,262 filed Aug. 2, 2001, which is a divisionalapplication of U.S. patent application Ser. No. 09/314,512, filed May19, 1999, which is entitled to benefit from prior U.S. ProvisionalPatent Application No. 60/086,601 filed May 22, 1998, which isincorporated in its entirety by reference herein.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to metal particles and methods ofagglomerating the same.

[0003] Efforts are always being made to improve the handling of metalpowder, such as tantalum powders. In particular, fine powders, forinstance, having particle sizes of 0.1-200 microns, can be quitedifficult to work with and thus, methods to agglomerate fine metalpowder have been developed, such as the method described in JapaneseKokai [1992]4-362101 for tantalum powder.

[0004] However, besides developing methods to agglomerate fine metalpowders, efforts have also been made to agglomerate such powders in sucha manner that flow properties and/or other desirable properties aremaintained or improved.

[0005] Accordingly, there is a demand to develop methods ofagglomerating fine metal particles such as tantalum powder, not only toaddress the problems of fine powders but also to lead to agglomeratedmetal particles that have desirable properties such as good flowproperties and improved pore size distribution.

SUMMARY OF THE INVENTION

[0006] In accordance with one aspect of the present invention, there isprovided a method to agglomerate metal particles, preferably tantalumand/or niobium particles, which includes the steps of combining avolatilizable or vaporizable liquid with the metal particles to form wetmetal particles. These wet metal particles are compacted and then driedto form a cake. The cake is then thermally agglomerated or heat treatedto result in the agglomerated metal particles.

[0007] In accordance with another aspect of the present invention, thereis provided metal particles, and especially tantalum and/or niobiumparticles having a flow rate of at least about 65 mg/sec. and animproved pore size distribution.

[0008] Further, the present invention relates to capacitor anodescontaining the tantalum and/or niobium powder of the present invention.

[0009] It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory only and are intended to provide further explanation of thepresent invention as claimed.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0010] An embodiment of the present invention relates to a method toagglomerate metal particles. The method includes the steps of combininga volatilizable or vaporizable liquid with the metal particles to formwet metal particles. The wet metal particles are compacted, and thensubsequently dried to form a cake. The cake is then heat treated toresult in the agglomerated metal particles.

[0011] For purposes of the present invention, the metal particles can beany type of metal particles. Examples of metal particles include, butare not limited to, metals, alloys, mixtures, and the like. Specificexamples include tantalum, niobium, iron, zinc, alloys containing any ofthe foregoing, and mixtures thereof. Preferably, the metal particlescomprise powders of niobium or tantalum, or alloys comprising tantalumand niobium.

[0012] The metal particles which are agglomerated by the methods of thepresent invention can be any particle shape or size, preferably, theparticles are in the form of a powder, and this powder generally hasparticle size ranges from about 0.1 micron to about 200 microns. Theshape of the metal particles can be any shape, such as angular, nodular,flaked, or any combination thereof. Preferably, the shape is nodular,especially when the metal particle is tantalum and/or niobium.

[0013] With respect to the method of agglomerating metal particles, thestep of combining a volatilizable or vaporizable liquid with the metalparticles to form wet metal particles can be done in any conventionalmanner which includes methods of simply mixing a solid with a liquid.For instance, simple stirring can be used as well as more sophisticatedmethods of blending and milling, such as with a mixer-muller.Alternatively, the liquid can simply be poured on top of a containercontaining the metal particles with or without mixing or stirring.

[0014] The volatilizable or vaporizable liquid can be any liquid whichis capable of these properties. Examples include, but are not limitedto, water, water-containing liquids, alcohols, aromatic-containingliquids, alkane-containing liquids, and the like. Preferably, thevolatilizable or the vaporizable liquid is aqueous in nature and morepreferably is water, and more preferably is deionized water. Anyelement/chemical helpful in controlling the sintering kinetics of thepowders at high temperatures can be added to the water at the desiredproportions.

[0015] Preferably, the amount of liquid combined with the metalparticles to form wet metal particles is an amount which is sufficientto wet the particles without forming a slurry. Preferably, the amount ofliquid contained with the metal particles is an amount which will resultin the formation of a paste. For instance, the amount of liquid presentwith metal particles having pores should be such that the liquid entersthe pores of the metal particles and most preferably, enterssubstantially all the pores of the metal particles. When the liquid isadded in an amount which forms a slurry, the liquid may exit the poresof the metal particles due to effects of gravity and the like. Thus, onepreferred way of combining a liquid with the metal particles is to addliquid in stages, such that when the initial addition of liquid has beenabsorbed into any pores of the metal particles that may exist, adetermination can then be made to add an additional amount of liquid.This staging of liquid introduction can occur up to a point where asmall amount of a liquid layer is formed on top of the metal particleswhich indicates that substantially all of the pores (if any exist) haveliquid in them and that any further addition of liquid could lead to theformation of a slurry. This liquid layer on top is preferably not morethan about 0.125 ml/cm² of container's square area. When the metalpowder comprises tantalum powder, for example, preferably not more thanabout 50 ml excess water is on top of the powder, when the powdercompletely fills a 20 cm×20 cm×5 cm pan.

[0016] When pores are present in the metal particles, in order to ensurethat the liquid has entered the pores of the metal particles, it ispreferred to let the liquid soak with the metal particles for a timesufficient to permit such absorption of the liquid into the pores of themetal particles. For instance, with respect to tantalum powder, it ispreferred to let the liquid soak into the powder for at least about fivehours, and more preferably, for at least about eight hours, even morepreferably from about five hours to about 16 hours. If, during thissoaking time additional liquid needs to be added, the liquid can beadded at any time in order to ensure full saturation or substantiallyfull saturation of any pores that may exist in the metal particles.Preferably, in the case of tantalum, the amount of liquid present byweight is from about 30% to about 40% by weight of the metal particlespresent, and more preferably, about 35% by weight based on the weight ofthe tantalum particles present. Similar amounts of liquid are expectedwith niobium powder. For other particles, the amount of liquid will be afunction of the particle size distribution of metal particles, andtherefore the amount of liquid present can be varying amounts.

[0017] Preferably an inorganic acid solution is part of the liquid whichis added or combined with the metal particles. Preferred inorganic acidcomprises phosphoric acid especially when the liquid is deionized waterand the metal particles are tantalum, niobium, or alloys thereof.Preferably, from about 10 ppm to about 200 ppm phosphorous by weight ofmetal particles is present, and to obtain this amount, a sufficientamount of phosphoric acid is present in the liquid and combined with thewet metal particles to obtain the amount of phosphorous in the liquid.The phosphorous can act as a sintering retardant. Other sinteringretardants can be used, and can depend on the metal particle sintered.

[0018] After the liquid has been combined with the metal particles toform wet metal particles, the wet metal particles are then compacted inorder to reduce or eliminate any air pockets between the particlesand/or liquid and to reduce the area between the particles. Preferably,the wet particles are compacted in such a manner that the metalparticles are closer to one another without forcing any liquid out ofthe pores that may be present in the pores of the metal particles.Compacting the wet metal particles may also increase the amount ofliquid in the pores of the metal particles. The most preferred means ofcompacting the wet metal particles involves vibrating a containercontaining the wet metal particles. Any means of vibrating the containercan be used, such as manually, or with any device capable of moving acontainer to create vibrating motions. Preferably, the compacting stageoccurs in a non-stick container, such as a “calphalon” tray or othersimilar type container which has the ability to prevent the “sticking”of material on the sides of the container. During the vibrating stage,additional liquid can be added and should preferably be added if theliquid layer that is preferably present on top begins to disappear.After vibrating, the wet metal particles should have the consistencythat is similar to wet cement which has just been applied to a sidewalkand smoothed and compacted. A most preferred consistency is theconsistency of a paste that is dispersed from a squeeze tube (e.g.,toothpaste). Preferably, the wet metal particles are compacted for atleast two minutes and more preferably, from about four minutes to about20 minutes.

[0019] After the compacting stage, it is preferred that the containerwith the wet metal particles stand still for a sufficient time to permitany water to separate from the wet metal particles. Preferably, thecontainer should sit for at least one hour, and any excess liquidseparating can be removed by any means, such as decanting.

[0020] After the compacting step, the compacted wet metal particles areformed into a cake by drying. Any means of drying the wet metalparticles formed into the cake can be used. For instance, the cake canbe dried with the use of a vacuum drying having a sufficient temperatureand/or pressure which will dry substantially all of the powder byremoving most, if not all of the liquid present. Preferably, the vacuumdrying occurs at a temperature of about 195° F. and about 40 torr vacuumfor about 10 hours or more, and preferably, for about 14 hours or more.

[0021] Once the metal powder cake is dried, the material is preferablyheat treated or thermally agglomerated. Preferably, this heat treatmentoccurs like any other heat treatment of metal powders. For example, thecake can be transferred onto a heat tray and subjected to heattreatment, which can be the heat treatment normally used with theparticular type of metal particles involved. In some situations, thetemperature of the heat treatment can be lowered because of theproperties obtained by using the method of the present invention. Forinstance, with respect to tantalum powder, the heat treatment ispreferably at a temperature of about 1300° C. for about 30 minutes.Other heat treatment temperatures and times can be used.

[0022] After heat treatment, the heat treated cake can be deagglomerated(for instance, by grinding or crushing or milling) to produce finepowder for any use. For instance, with respect to tantalum and niobiumpowders, the powders can be formed into capacitor anodes or for otheruses associated with tantalum and niobium powder.

[0023] With respect to the flaked metal powders, especially tantalum andniobium flaked powder, the processes of the present invention arepreferably conducted by first heat treating the flaked metal powder andthen crushing or grinding the heat treated flaked powder to result inagglomerates. Preferably, these agglomerates have the size of from about50 to about 100 microns in size. These agglomerates are then subjectedto the agglomeration process described above with the addition of avolatilizable or vaporizable liquid and so on. After the heat treatingof the agglomerated cake comprising the flaked metal powder, the cake isthen crushed again to form agglomerates and these agglomeratespreferably have the improved properties described herein, includingimproved green strength.

[0024] A combination of properties can be achieved by the presentinvention. In particular, the flow properties of the metal powder aswell as the DF value of the capacitor anodes, in particular, thetantalum powder, can be improved. In particular, with respect totantalum, a flow of at least about 65 mg/sec and more preferably, fromabout 65 to about 400 mg/sec can be obtained, and more preferably, fromabout 159 mg/sec to about 250 mg/sec. In combination with these flowproperties, a lower DF value can be obtained. Also, metal powdersagglomerated by the present process can have excellent Scott Densities.For instance, the Scott Densities can increase at least 10% andpreferably increase at least 25% and more preferably increase at least35% or more compared to metal powder not agglomerated. Preferably, theScott Densities are at least about 20 g/inch³, and more preferably, atleast 22 g/inch³, and even more preferably, from about 20 to about 40g/inch³.

[0025] Another benefit of the present invention is the ability toincrease the pore size distribution of the metal particles (preferablythe metal particles like tantalum and/or niobium), after being pressedand sintered into an anode. Increasing the pore size distribution of thepressed and sintered anode can be very beneficial with respect tocapacitor anode for tantalum and/or niobium where typically Mn(NO₂)₃ iscoated onto the anode and then the material is pyrolized. This increasedor improved coverage leads to beneficial properties such as improvedflow and/or the DF values. As shown in the Figures, the pore sizedistribution of the anodes made from the powders of the presentinvention have large pores (greater in size) that do not exist in anodesmade with unagglomeraed powder or powders agglomerated by other methods.Also, the number of overall large pores in greater for the anodes of thepresent invention. The means of making the powder, particularly metalpowder, into a capacitor anodes is known to those skilled in the art andsuch methods such as those set forth in U.S. Pat. Nos. 4,805,074,5,412,533, 5,211,741, and 5,245,514 and European Patent Application Nos.0 634 762 A1 and 0 634 761 A1 can be used and are incorporated in theirentirety herein by reference.

[0026] The present invention will be further clarified by the followingexamples which are intended to be purely exemplary of the presentinvention.

EXAMPLES

[0027] Samples 1 and 2 were processed using tantalum powder basic lots,properties of which are described in Table A. Each sample was preparedusing 12 lbs. of basic lot tantalum. Each basic lot was blended with 2.9gms. of Ammonium Hexa Fluoro Phosphate (NH₄PF₆). NH₄PF₆ provided thesource of phosphorous and the amount provides 100 ppm of phosphorous byweight in the powder. Each blended sample was heat treated at 1325° C.for 30 minutes at a vacuum level of less than 5 microns of mercury.Samples 1 and 2 represent two separate heat treated batches. Heattreated material which was in the form of cakes was crushed and screenedusing 70 mesh (US Sieve) screen. The −70 mesh powder was blended withmagnesium to have a magnesium content of 2% by weight. Magnesium blendedtantalum powder was deoxidized by heating at 950° C. This deoxidationstep was conducted to lower the oxygen content of the tantalum powder toreasonable level. The deoxidized tantalum powder was then treated withnitric acid, hydrogen peroxide and deionized water to remove theresidual magnesium and the magnesium oxide generated during thedeoxidation process. The tantalum powder was further rinsed withdeionized water until a conductivity of less than 10 microohms/cm wasattained in the DI water. The rinsed tantalum powder was dried using avacuum dryer. A representative sample of the dried tantalum powder wastaken and analyzed for physical, chemical electrical properties of thepowder, and pore size distribution using mercury porosimetry equipment.The results are shown in Table 1. The electrical properties wereevaluated using the following procedure:

[0028] [1] Anode Fabrication:

[0029] (a) Haberer Press

[0030] (1) non-lubed powder

[0031] (2) size-0.1235″ dia×1928″ length

[0032] (3) Dp=5.5 g/cc

[0033] (4) powder wt=207.5 mg

[0034] [2] Anode Sintering:

[0035] (a) NRC Furnace;

[0036] 1335 Deg C.*10(“A” ramp)

[0037] (b) N=32 anodes of each powder

[0038] [3] 30V Ef Evaluation:

[0039] (a) Anodization:

[0040] (1) Two Formations (form each singer separately)

[0041] N=8 anodes (one tree) per sample

[0042] (1)tree/sample*(1)sinter*(8)sample=8 trees

[0043] +C606 stds

[0044] (2) Electrolyte; (0.6% H3P04@83 Deg. 1.86 mmho)

[0045] (3) Constant current density: 337.5 ma/g

[0046] (4) Terminal Voltage=30.0 VDC+/−0.03

[0047] (5) Terminal Voltage Time=300 min−0/+5 min

[0048] (b) DC Leakage:

[0049] (1) Charge E=21.0+/−0.02

[0050] (2) Charge Time=30 sec & 120 sec

[0051] (3) DCL Test Electrolyte=10% H3P04@21 Deg C.

[0052] (c) Capacitance/DF:

[0053] (1) Capacitance Test Electrolyte=18% H2S04@21 Deg C.

[0054] (2) Bias=2.5 VDC

[0055] (3) Frequency=120 Hz

[0056] (4) Series Capacitance

[0057] (5) GenRad #1658

[0058] [4] Mercury Porosimetry Evaluation:

[0059] Retained sintered anodes were sent to Micromeritics InstrumentCorporation, One Micromeritics Drive, Norcross, Ga. 30093. The pore sizedistribution was determined at The Materials Analysis Laboratory ofMicromeritics using the AutoPore III 9420 and the following settings:Penetrometer: 33-(14) 3 Bulb, 0.412 Stem, Powder Pen. Constant: 10.970μL/pF Adv. Contact Angle: 130.000 degrees Fixed Pen. Weight: 63,6614 gRec. Contact Angle: 130.000 degrees Fixed Stem Volume 0.4120 mL HgSurface Tension: 485,000 dynes/cm Fixed Max. Heat Pressure 4.6800 psiaHg Density: 13.5335 g/mL Pen. Volume 3.1251 mL Sample Weight 1.6879Assembly Weight 103.8746 g Low Pressure: Evacuation Pressure: 50.000μmHg Evacuation Time: 5 mins Mercury Filling Pressure: 20.05 psiaEquilibration Time: 10 secs High Pressure: Equilibration Time: 10 secsBlank Correction by Formula Fixed by Micromeritics

[0060] Sample 3 was prepared using the basic lot described in Table A.Two 27.5 lbs. of the basic lot powder were placed in two 5 gallonstainless steel buckets. Phosphorous dopant solution was prepared byadding 10 ml. of 85% reagent grade phosphoric acid (85% solution) into2000 ml DI water. 4443 ml of DI water was mixed with 551 ml ofphosphorous dopant solution. This solution represents 40% by weight ofwater for 27.5 lbs. of tantalum powder. This solution containing 100 ppmby weight of phosphorous. The 4994 ml of the mixed DI water was added tothe tantalum powder by transferring the solution to the stainless steelbucket containing the tantalum powder. Similarly, another 4994 ml DIwater+phosphoric acid solution was prepared and transferred to thesecond stainless steel bucket containing the tantalum powder. The powderwas soaked for 20 hrs. The soaked tantalum powder was transferred totantalum heat treat trays by scooping the wet powder using a stainlesssteel scoop. Tantalum trays containing the wet tantalum powder weretransferred to a vacuum dryer for drying. Powder was dried in a vacuumdryer at 185° F. and about 50 torr vacuum for 48 hrs. After drying, thetantalum trays containing the dried powder was transferred into a heattreat furnace. The powder was heat treated at 1345° C. for 30 minutes ata vacuum level of less than 5 microns of mercury. Heat treated cakeswere crushed and screened using a 50 mesh (US Sieve). The −50 meshpowder was blended with 2% magnesium and deoxidized and furtherprocessed as described for samples 1 and 2.

[0061] Samples 4 and 5 of agglomerated tantalum powder were prepared asfollows. The basic lot tantalum powder used for the two samples is shownin Table A. In each case, fifty pound increments of tantalum powder wereplaced in stainless steel buckets. Total tantalum powder used was 250lbs. for both samples 4 and 5. 6944 ml of deionized water was mixed with1002 ml. of phosphorous dopant solution described above in Example 1.7966 ml of the solution was added to each bucket. This solutionrepresent 35% by weight of tantalum powder and it also contains 100 ppmby weight of phosphorous. The water was allowed to soak into thetantalum powder for approximately 12 to 16 hours. Afterwards,approximately 8.1 pounds of the wet tantalum powder was transferred to adrying tray. Drying trays consisted of square cake pans (8×8×2 inches)from “Calphalon.” Calphalon supplies the bakeware with an advancednonstick coating system. The calphalon tray containing the wet tantalumpowder was transferred to a vibrating unit. The vibrating unit consistedof a vibrating table fitted with an air operated motor working at apressure of 60 psi. Additional deionized water in an amount of 150 mlwas added to each tray and was vibrating for approximately four minutes.After vibrating, the trays were allowed to sit for at least sixtyminutes for any water to separate. Any water which separated wasdecanted. Afterwards the drying trays were transferred to a vacuumdryer. The commercial vacuum drying was purchased from STOKES VACUUMInc., model number 338J. The material in the Calphalon trays was driedfor approximately 14 hours at about 195° F. and 50 torr pressure. Thedried tantalum powder was then transferred to a tantalum tray for heattreatment. The heat treatment was conducted at approximately 1320-1330°C. for about 30 minutes. The cakes were then transferred to a batch canfor milling and were milled and screened using 70 mesh (US Sieve)screen. −70 mesh portion of the material was deoxidized and acid leachedas described in Example 1. Samples of the final product were analyzedand the data is shown in Table 1.

[0062] Samples 7-10 were processed using tantalum basic lots of highersurface area. Typical analysis of the basic lot used is described inTable A.

[0063] Samples 9 and 10 were processed using the conventional process.Typically 12 lbs. of tantalum powder was blended with ammoniumhexafluorophosphate to add 100 ppm by weight phosphorous. The blendedpowder was heat treated in the range of 1200-1265° C. for 30 minutesunder vacuum. The heat treated cakes were processed to final powder asdescribed for sample 1. The deoxidation for these powders were conductedat 850° C. with 2.5% magnesium added. The electrical evaluationprocedure for these samples is described below.

[0064] [1] Anode Fabrication:

[0065] (a) Haberer Press

[0066] (1) non-lubed powder

[0067] (2) size-0.1545″ dia×0.1363″ length

[0068] (3) Dp=4.5 g/cc

[0069] (4) powder wt=188 mg

[0070] [2] Anode Sintering:

[0071] (a) NRC Furnace; 1265 Deg C.*10(“A” ramp)

[0072] (b) N=34 anodes of each powder sample

[0073] [3] 30V Ef Evaluation:

[0074] (a) Anodization:

[0075] (1) One Formation

[0076] N=8 anodes (one tree) per sample

[0077] (2) Electrolyte; (0.6% H3P04 @83 Deg. 2.86 mmho)

[0078] (3) Constant current density: E251 Test Current (337.5 ma/g)

[0079] (4) Terminal Voltage=30.0 VDC+/−0.03

[0080] (5) Terminal Voltage Time=300 min−0/+5 min

[0081] (6) Soak 25 C for 30 minutes

[0082] (7) 100° C. over for 30 minutes

[0083] (b) DC Leakage:

[0084] (1) Charge E=21.0+/−0.02

[0085] (2) Charge Time=30 sec & 120 sec

[0086] (3) DCL Test Electrolyte=10% H3P04@21 Deg C.

[0087] (c) Capacitance/DF:

[0088] (1) Capacitance Test Electrolyte=18% H2S04@21 Deg C.

[0089] (2) Bias=2.5 VDC

[0090] (3) Frequency=120 Hz

[0091] (4) Series Capacitance

[0092] Microporosimety evaluation using the sintered anodes wasconducted at Micromeitics using the AutoPore III 9420.

[0093] Samples 7 and 8 were prepared using the basic lot described inTable A. Sample 7 was prepared by soaking 24 pounds to tantalum with 25%by weight of deionized water containing phosphorous dopant solution toprovide 100 ppm by weight of phosphorous. The powder was soaked for 16hours. Soaked powder was transferred to four Calphalon trays andadditional 300 to 450 ml of deionized water was added. The wet powderwas vibrated from four minutes using the vibrating table. Aftervibrating, the trays were allowed to sit for at least sixty minutes forany water to separate. Any water which separated was decanted.Afterwards, the drying trays were transferred to a vacuum dryer. Thecommercial vacuum dryer was purchased from STOKES VACUUM Inc., modelnumber 338J. The material in the Calphalon trays was dried forapproximately 14 hours at about 196° F. and 50 torr pressure. The driedtantalum powder was then transferred to a tantalum tray for heattreatment. The heat treatment was conducted at approximately 1265° C.for about 30 minutes. The cakes were then transferred to a batch can formilling and were milled and screened using 70 mesh (US Sieve) screen.−70 mesh portion of the material was deoxidized using 2.5% magnesium at850° C. and acid leached as described in Example 1. Samples of the finalproduct were analyzed and the data is shown in Table 1.

[0094] Sample 8 was prepared by soaking 24 pounds of tantalum with 35%by weight of deionized water containing phosphorous dopant solution toprovide 100 ppm by weight of phosphorous. The powder was soaked for 16hours. Soaked powder was transferred to four Calphalon trays andadditionally 150 to 235 ml of deionized water was added. The wet powderwas vibrated for four minutes using the vibrating table. Aftervibrating, the trays were allowed to sit for at least sixty minutes forany water to separate. Any water which separated was decanted.Afterwards, the drying trays were transferred to a vacuum drying. Thecommercial vacuum dryer was purchased from STOKES VACUUM Inc., modelnumber 338J. The material in the Calphalon trays was dried forapproximately 14 hours at about 195° F. and 50 torr pressure. The driedtantalum powder was then transferred to a tantalum tray for heattreatment. The heat treatment was conducted at approximately 1200° C.for about 30 minutes. The cakes were then transferred to a batch can formilling and were milled and screened using 70 mesh (US Sieve) screen.−70 mesh portion of the material was deoxidized using 2.5% magnesium at850° and acid leached as described in Example 1. Samples of the finalproduct were analyzed and the data is shown in Table 1. TABLE A Startingmaterial for various samples (basic lots) Samples Samples 1 and 2 Sample3 Sample 4 Sample 5 7-10 Weights 26 lbs. 51.5 lbs. 250 lbs. 250 lbs. 80lbs. FSS Modified 0.41 0.39 0.4 0.42 0.32 (microns) Scott Density 13.521.9 14 13.9 12.6 (grams/inch3) C (ppm) 22 4 16 17 18 O (ppm) 6253 71446343 6048 7026 N (ppm) 25 151 25 23 26 Hydrogen 1585 1078 1488 1360 1520(ppm) BET 2.25 1.9 1.81 2.22 2.80 (meter2/gm)

[0095] The material was then pressed to form a capacitor anode in thefollowing manner:

[0096] The powder was pressed into 0.1235″ dia×1928″ length anodes at apress density of 5.5 gm/cc. The pressed anodes were sintered at 1335° C.for 10 minutes followed by anodization at 30 v. using H₃PO₄ electrolyte.The anodized anodes were tested for capacitance and DC leakage, pressdensity, and shrinkage.

[0097] Tantalum powder was also processed to make 300 mf 10V solidcapacitor and the DF values of the solid capacitor were measured.

[0098] The flow rate was determined by a die fill test which involved astand having 10 holes, ⅛ inch diameter evenly spaced along the centerline of the bar length. The die fill procedure was done in a room with arelative humidity of less than 70% and a temperature at normal roomtemperature. 40 grams of metal powder, in this case, tantalum powder,were placed in a hopper which passed over the 10 holes of the standwherein powder flows into the holes as the hopper passes over them. Aslide bar is located underneath the stand so as to cover each of the tenholes to prevent the powder from falling out of the stand. There are 4tests involved in determining flow rate wherein a hopper is passed overthe ten holes with an even 2 sec. pass, 4 sec. pass, 6 sec. pass, and an8 sec. pass, wherein during each pass the hopper is opened so that thepowder flows over the 10 holes. After each of the passes, the amount ofpowder in the holes is weighed and eventually calculations are madedetermining the flow based on mg/sec.

[0099] The Table below sets forth the various parameters of each of thesamples made and tested. As can be seen from the Table and Figures, theflow rate and the pore size distribution of the powders of the presentinvention were unexpectedly superior to unagglomerated tantalum powderand to agglomerated tantalum powder formed by a different process. Datafor the 52,000 cv/gm powder samples Sample ID 774-9.4M 7774-16.4M7549.70-M 110395 110396 Process No Preagglom No Preagglom Non-VibratedPresent Inv. Present Inv. Sample 1 Sample 2 Sample 3 Sample 4 Sample 5Weights 9.4 lbs. 9.5 43.6 lbs. 233.8 lbs. 228.3 lbs. FSS Modified 1.001.05 3.29 2.94 2.63 (microns) Scott Density 19.0 20.2 25.1 27.8 26.3(grams/inchs) C (ppm) 195 40 32 20 18 O (ppm) 4,070 3,123 3,109 3,3103,514 N (ppm) 214 121 166 66 57 H (ppm) 87 83 58 53 53 P (ppm) 101 122109 167 177 Screens +60 mesh 0 0 1.9 0 0 −60 + 100 mesh 2.6 2.8 37.910.4 9.6 −100 + 200 mesh 19.5 18.7 31.1 38.2 35.7 −200 + 325 mesh 17.716.3 13.8 16.6 16.9 −325 mesh 60.2 62.2 15.1 34.8 37.8 Flow mg/s 37 37235 182 175 1335C/30V Cap cv/g 60,246 55,355 54,926 52,734 55,329Shrinkage (%) 2.9 2.8 2.5 1.2 1.6 Sint. Den. 5.8 5.8 5.9 5.7 5.7(grams/cc) DCL na/cf 0.34 0.62 0.18 0.21 0.25 Data for highercapacitance powders Present Inv. Present Inv. No Agglom No Agglom.Process Sample 7 Sample 8 Sample 9 Sample 10 Weights 7.5 lbs. 8.3 lbs.11 lbs. 10 lbs. FSS 1.61 1.4 0.58 0.67 Scott Density (g/in) 26.7 23.616.3 17.4 C (ppm) 22 32 26 36 O (ppm) 5,762 5,335 6,368 5,057 N (ppm) 2726 67 58 H (ppm) 200 227 207 200 P (ppm) 36 57 101 43 Screens +60 0 00.5 0 −60 + 100 12.8 9.8 4.4 5.9 −100 + 200 36.5 36.6 28.4 28.3 −200 +325 19.2 19.9 31.8 26.7 −325 31.5 33.7 34.9 39.1 Flow mg/s 78 56 4.7 5.9Press density 4.5 gms/cc 1265C/30V Cap cv/g 80,135 83,282 85,372 81,752Shrinkage 2 2.4 3.7 2.5 Sint. Den. 4.7 4.7 4.9 4.8 DCL na/cv 0.27 0.260.34 0.31

[0100] As shown in FIGS. 1-4, anode samples 4 and 5 and 7 and 8 madefrom powders agglomerated by the method of the present invention hadlarger sizes that didn't exist in the remaining samples and also had ahigher number of large pores than the remaining samples. Accordingly,the pore size distribution was considerably better for the samples ofthe present invention in view of these two improved parameters. Theseimproved parameters are predictive indicators with regards to a lowerDissipation Factor for the anode and other beneficial properties.

[0101] Other embodiments of the present invention will be apparent tothose skilled in the art from consideration of the specification andpractice of the present invention disclosed herein. It is intended thatthe specification and examples be considered as exemplary only, with atrue scope and spirit of the present invention being indicated by thefollowing claims.

What is claimed is:
 1. A method to agglomerate tantalum or niobiumparticles or both comprising: a) combining a volatilizable orvaporizable liquid with particles comprising tantalum, niobium, or bothto form wet particles; b) compacting the wet particles; c) drying thewet compacted particles to form a cake; and d) heat treating the cake.2. The method of claim 1, wherein said compacting is accomplished byvibrating said wet particles in a container.
 3. The method of claim 1,wherein said compacting is accomplished by applying pressure to said wetparticles.
 4. The method of claim 1, wherein said liquid is water. 5.The method of claim 1, wherein said water is deionized water.
 6. Themethod of claim 1, wherein before said compacting, said particles soakin the liquid for at least five hours.
 7. The method of claim 1, whereinbefore said compacting, said particles soak in the liquid for at leasteight hours.
 8. The method of claim 1, wherein said drying occurs for atleast 10 hours.
 9. The method of claim 1, wherein said drying occurs forat least 14 hours.
 10. The method of claim 1, wherein said liquid ispresent in an amount of from about 30% to about 50% by weight ofparticles.
 11. The method of claim 1, wherein said liquid is added in anamount of about 40% by weight of particles.
 12. The method of claim 1,wherein the cake is deagglomerated after heat treating.
 13. The methodof claim 1, said particles have pores, and wherein before saidvibrating, the particles soak in the liquid for a time sufficient toallow the liquid to substantially fill the pores of the particles. 14.The method of claim 1, wherein the particles are tantalum particles. 15.The method of claim 1, wherein the particles are niobium particles. 16.The method of claim 1, wherein the particles comprise tantalumparticles.
 17. The method of claim 1, wherein the metal particlescomprise niobium particles.
 18. The method of claim 1, wherein theliquid comprises water.
 19. The method of claim 1, wherein the liquidcomprises water and phosphoric acid.
 20. The method of claim 1, whereinthe liquid comprises water and from about 10 ppm to about 100 ppm ofphosphorous.
 21. The method of claim 1, wherein the liquid compriseswater and an inorganic acid.
 22. The method of claim 1, wherein theliquid is present in an amount of from about 10% to about 50% by weightof particles.
 23. The method of claim 1, wherein the liquid is presentin an amount to form a paste consistency with the particles.
 24. Themethod of claim 1, further comprising the step of adding additionalvolatilizable or vaporizing liquid to the container while the containeris being vibrated.
 25. The method of claim 1, wherein said drying isaccomplished in a vacuum dryer.
 26. The method of claim 1, wherein saiddrying occurs at a temperature of from about 180° F. to about 225° F.27. The method of claim 1, wherein said drying occurs at a temperatureof from about 180° F. to about 225° F. and a vacuum pressure of fromabout 20 torr to about 50 torr.
 28. The method of claim 1, wherein aliquid drying forms on top of the wet particles, before or aftercompacting.
 29. The method of claim 28, wherein about 0.125 ml/cm² ofwater forms on top of the wet particles based on the square area of acontainer containing the particles.
 30. Agglomerated particles obtainedby the method of claim
 1. 31. Agglomerated particles obtained by themethod of claim
 2. 32. Agglomerated particles obtained by the method ofclaim
 3. 33. Particles comprising tantalum, niobium, or both, having aflow rate of at least about 65 mg/sec and a pore size distributiongreater than unagglomerated particles.
 34. The particles of claim 33,wherein said particles have a flow rate of at least about 100 mg/sec.35. The particles of claim 33, wherein said particles have a flow rateof at least about 150 mg/sec.
 36. The particles of claim 33, whereinsaid particles have a flow rate of at least about 175 mg/sec.
 37. Theparticles of claim 33, wherein said particles have a flow rate of atleast about 200 mg/sec.
 38. The particles of claim 33, wherein saidparticles comprise niobium.
 39. The particles of claim 33, wherein saidparticles comprise tantalum.
 40. The particles of claim 33, wherein saidpore size distribution is greater than unagglomerated particles by atleast 10% with respect to greater diameter pores.
 41. The particles ofclaim 33, wherein said particles are nodular tantalum powder.
 42. Theparticles of claim 33, wherein said particles are nodular niobiumpowder.
 43. The particles of claim 41, wherein said particles have aScott Density of at least 20 g/inch³.
 44. The particles of claim 41,wherein said particles have a Scott Density of about 20 g/inch³ to about40 g/inch³.
 45. A capacitor component comprising the tantalum powder ofclaim
 39. 46. A capacitor component comprising the niobium powder ofclaim
 38. 47. The capacitor component of claim 45, wherein saidcomponent is a capacitor anode.
 48. The capacitor component of claim 46,wherein said component is a capacitor anode.
 49. A method to agglomeratemetal particles comprising: a) combining a volatilizable or vaporizableliquid with metal particles to form wet particles; b) compacting the wetmetal particles; c) drying the wet compacted metal particles to form acake; and d) heat treating the cake.
 50. A method to agglomerate metalparticles comprising: a) combining a volatilizable or vaporizable liquidwith particles comprising wet metal particles; b) vibrating the wetparticles; c) drying the wet metal particles to form a cake; and d) heattreating the cake.